Servers that provide games to portable devices via communication networks have been widespread in recent years. Games provided by such servers include, for example, reward winning games (including those generally known as “Gachagacha (registered trademark in Japan)”) (for example, refer to Japanese Unexamined Patent Publication No. 2012-221132). A reward winning game is a game in which a reward selected from a set of rewards by random lottery is given to a user.
Recently, a package-type reward winning game has been proposed in which a list showing the kinds of rewards and the number of rewards to be given is presented in advance to the user and rewards selected from the list are given to the user without duplication among the rewards. More specifically, in the package-type reward winning game, a package (a set or group) of rewards is made available for each user, and any reward once given to the user is deleted from the package so that the same reward will not be given to the user in a duplicate manner. The package-type reward winning game has the feature that no duplication occurs among the rewards won and that a user can eventually receive even rare rewards without fail.